A very good illustration of the algorithm was posted by @deepsand in an earlier SEO89: thread:
Because of the massive number of iterations involved, it is practically impossible to calculate one's own PageRank since one has really no real idea how many pages are linking, and how many links are in all those pages (combined).
We need also to bear in mind that in light of quality considerations, this algorithm is just a starting point. Brin/Page bring up this consideration in point #8, which has clearly been the path that Google has taken (to consider advertisers). PR may be calculated against the algorithm, but for SERPs it may have little or no bearing when all other factors are weighed in.